You can get an Impure Hogyoku by using a Time Remnant, a rare item obtainable in Invasions, Incursions and Time Gates. The chance of getting a Time Remnant are:

• Invasions (F/D ranks) – 0.1%
• Incursions – 0.1%
• Invasions (B rank) – 0.2%
• Time Gate – 0.6% (only if your team wins)
  • Note : After 45 Wins in Time Gates, you are guaranteed to get a Time Remnant.
• Weekly quests
• Dr. Hydrogen's Scrapper Machine (you can get a Time Remnant or an Impure Hogyoku)
• Trading

How we trade: 

After buying, chat me your trading hub server and username and i will be there🙌